The global average concentration of carbon dioxide (CO₂) in the atmosphere is tracked and updated monthly, capturing both seasonal and interannual trends. Data are drawn from paired, weekly samples collected at 40 sites in the remote marine boundary layer around the globe.
The sawtooth pattern demonstrates the fluctuation of atmospheric concentration of carbon dioxide over seasonal cycles, driven largely by the terrestrial biosphere. There is an overall upward trend since data collection began. Global monthly average concentrations of carbon dioxide have risen steadily from 339 parts per million in 1980 (averaged over the year) to 415 parts per million in 2021, an increase of more than 20% in 42 years.
Carbon Dioxide in the Atmosphere is Increasing
The amount of CO₂ in the atmosphere has increased more than 20% in less than 42 years, owing largely to human activities, and representing well over 50% of the total increase in atmospheric carbon dioxide since the onset of the industrial revolution (1750).
Why It's Important
Carbon dioxide concentration is an important measure of how human activity has increased the heat-trapping capacity of the atmosphere.
This indicator can inform carbon emissions policies at national and international levels.
About Atmospheric Carbon Dioxide
Greenhouse gases such as carbon dioxide trap heat in the atmosphere. Increasing concentrations of these gases have driven an increase in global temperatures. The Annual Greenhouse Gas Index (AGGI) shows that over the past decade, increases in carbon dioxide are responsible for about 81% of the increase in the heat-trapping capacity of the atmosphere. Although the atmospheric concentration of carbon dioxide fluctuates over seasonal cycles, as illustrated by the saw-tooth pattern in the graph, the overall trend has been a steady increase since data collection began. Global monthly average concentrations of carbon dioxide have risen from around 339 parts per million in 1980 (averaged over the year) to 415 parts per million in 2021, an increase of more than 20%.
The National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Laboratory has measured carbon dioxide and other greenhouse gases for several decades through a globally distributed network of about 70 air sampling sites, including the Mauna Loa Observatory in Hawai’i. The data for this indicator come from a subset of about 40 of these sites located in isolated regions of the ocean.